Large-capacity refrigeration cycle apparatuses require a large-capacity compressor. Patent literature 1 discloses a method for increasing the capacity of a refrigeration cycle apparatus by connecting a plurality of compressors in parallel. FIG. 9 shows a compressor disclosed in the patent literature 1.
As shown in FIG. 9, a connected compressor 700 includes a first compressor 701a and a second compressor 701b. An upper portion of the first compressor 701a and an upper portion of the second compressor 701b are connected to each other by a pressure equalizing pipe 707. A bottom portion of the first compressor 701a and a bottom portion of the second compressor 701b are connected to each other by an oil equalizing pipe 708. Since a lubricating oil can flow from the first compressor 701a to the second compressor 701b and vice versa through the oil equalizing pipe 708, the amount of lubricating oil does not become excessive or deficient in each of these compressors.
In the meantime, research and development have been conducted actively on energy saving for refrigeration cycle apparatuses for water heaters and air conditioners. As one of the technologies for energy saving, expander-integrated compressors are being developed. The expander-integrated compressor is a fluid machine in which a compressor and an expander are coupled to each other by a shaft. FIG. 10 shows an expander-integrated compressor disclosed in patent literature 2.
As shown in FIG. 10, an expander-integrated compressor 800 includes a closed casing 802, a compression mechanism 801 disposed at an upper portion in the closed casing 802, and an expansion mechanism 804 disposed at a lower part in the closed casing 802. The compression mechanism 801 and the expansion mechanism 804 are coupled to each other by a first shaft 803 and a second shaft 805. An oil pump 808 for supplying a lubricating oil to the compression mechanism 801 is provided between the compression mechanism 801 and the expansion mechanism 804. The power recovered from a refrigerant at the expansion mechanism 804 is transferred to the compression mechanism 801 via the shafts 803 and 805. Thereby, the load on a motor for driving the compression mechanism 801 can be reduced.
Citation List
Patent Literature
PTL 1: JP 7(1995)-35045 A
PTL 2: JP 2008-38915 A